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This is Fig. 19 from the 2011 GENOPT paper. This slide shows a typical local buckling mode from a STAGS model of part of the axially compressed truss-core sandwich cylindrical shell. (Local buckling in this particular model occurs in the outer skin and therefore is mostly hidden by the inner skin in this picture.)
The axial length included in this model is FACLEN x LENGTH = 0.05 x 109 = 5.45 inches. Four 22-segment modules of the type shown in Fig. 4 of the 2011 GENOPT paper, are included in this particular local buckling model.
“Noodles” and “noodle gaps” are included in this model. The STAGS 480 finite element is used for the shell segments and the STAGS 928 finite elements are used for the “noodles”, which are treated as discrete stringers located in the “noodle gaps” (see the prevous slide).
This particular STAGS model has a much smaller radius (7.815 inches) than the radius (78.15 inches) of the cylindrical shell that is the subject of the rest of the 2011 GENOPT paper. The much smaller radius is used in this figure so that the viewer can easily see that the STAGS model for local buckling includes the overall curvature of the cylindrical shell.
The axial compression is applied by uniform end shortening in such a way that the pre-buckled state of the shell is uniform axial compression with only very small localized edge effects that do not affect the buckling behavior (See Fig. 1g of the 2011 GENOPT paper).
In order to see figures referred to here but not shown here, please download the 2010 GENOPT paper from this website.
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